水稻QHB基因对籽粒发育调控的分子机理研究

Increasing crop yield is one of the most important goals of plant science research. Grain size is a major determinant of grain yield in cereals and is a target trait for both domestication and artificial breeding. QHB was reported to be involved in the specification and maintenance of the root apical meristem (RAM) stem cells of rice. Here, we showed that QHB (Quiescent center specific Homeobox) in rice controls grain size. Using transformants carrying the QHB promoter-GUS (longer than reported), we found that QHB not only expressed in the central cells of a quiescent center (QC) of the root, but also QC of the stem and developing seed. We also produced transformants that overexpress QHB or knock-down QHB in rice. High expression of QHB transformants did not form crown roots Lethal, but weak transformants could produce shorter but wider grains. We fused VP64 transcription activator domain to the N terminal of QHB to produce the artificial Hybrid transcription factor VP-QHB, which could convert the QHB from suppression activity to activation activity. VP-QHB transformants could produce longer and wider grains. On the basis of these observations, we propose that the QHB gene is involved in the grain shape regulation in rice by mechanisms that not clear. Here, with further molecular genetic approach, we want to clear biological function and regulation network of QHB and to provide more evidences for the mechanism of grain size determination.

水稻粒型与产量密切相关，发掘控制水稻粒型基因对提高水稻产量十分重要。我们的研究发现水稻WOX转录因子家族基因QHB不仅调控水稻根分生组织的分化与再生还参与粒型调节。GUS染色表明QHB可以在茎尖分生组织和发育中的颖壳中表达；QHB过表达植株籽粒长度显著变短的同时宽度显著增加，而融合了转录激活功能域基序VP64人工合成转录因子VP-QHB则可以使籽粒变得既长又宽。本研究希望在此研究基础上，利用RNAi和CRISPR技术敲除QHB基因，明确QHB的生物学功能；结合RNA和ChIP-exo测序技术系统的分析QHB调控网络，阐明QHB粒型调控分子机理；同时发掘参与粒型调控下游基因，为其在水稻改良中的应用奠定基础。